PORTLAND — Nearly $33 million in damage will be done to buildings along Portland’s low-lying – and high-traffic – Commercial Street area by 2050 because of steady sea level rise, a city architects group announced Tuesday.

That figure jumps to about $111 million by 2100. By that year, parcels where $46.4 million worth of buildings stand today will be “inundated on a daily basis (by high-tide flooding) if no changes are made.”

The projections were part of a report released Tuesday by the Portland Society for Architecture, and compiled by the Scarborough-based Catalysis Adaptation Partners.

As part of a news conference at Portland’s Ocean Gateway facility, the organizations also announced a two-day “Waterfront Visions: 2050” symposium on Nov. 7-8 to brainstorm plans to avoid the potentially catastrophic economic effect of the sea-level rise.

The study looked exclusively at the threat to buildings along Portland’s bustling waterfront Commercial Street. It did not evaluate the potential for flooding along Back Cove and the city’s Bayside neighborhood, also considered danger zones for storm surges and sea-level rise.

For the purposes of the report, researchers with Catalysis assumed a two-foot sea level rise by 2050 and a four-foot rise by 2100.

“We used two and four feet because those are the midlevel values of sea-level rise expected over the next century (by the Intergovernmental Panel on Climate Change),” said JT Lockman, vice president of environmental planning for Catalysis. “There are many people who are worried that if the ice sheets that are over land melt or slide out onto the ocean, you might be looking at six or eight feet by 2100.”

The report also considered storm surges based on the “midlevel” sea-level rise scenarios, finding that a 100-year storm – with precipitation amounts statistically expected to have a 1 percent chance of occurring in any given year – would do $16 million in damage to buildings in 2050 and $26.4 million in damage to buildings in 2100.

Meteorologist Mike Kistner of the National Weather Service in Gray later said that, for Portland, a 100-year storm means 7.49 inches of rainfall from a midnight-to-midnight 24-hour period. Since 1900, Kistner said Portland has weathered four 100-year storms, in 1954, 1962, 1991 and 1996.

The greatest amount of rain Maine’s largest city saw over a daylong tracking period in the last decade was 5.3 inches on Nov. 14, 2009, he said.

Alan Kuniholm, president of the Portland Society of Architects, said the upcoming symposium is intended to continue in earnest conversations about building alterations and infrastructure improvements that could help the city brace against the higher tides, storm surges and resultant floodings.

“It will put any low-lying areas in coastal communities at risk,” he said. “It’s not surprising that many of the buildings seen as at risk are already currently flooding on a regular basis.”

Lockman, whose organization has compiled sea-level rise reports for communities up and down the Eastern Seaboard, said Portland is among the cities most threatened by the rising water.

“Portland has a challenge in that it has multiple buildings on piers out over the water,” he said. “That only happens in cities that developed in the 18th and 19th centuries. Newer cities really don’t have that, so cities like Portland are in greater jeopardy.

“Even in weather that’s not that bad, areas of Commercial Street are already seeing water coming very close to buildings,” Lockman continued. “I’ve taken pictures near Back Cove where seawater is coming up through the drains even on nice days.”

Lockman also tried to distance Tuesday’s report from any political debate over climate change or its causes.

“I think people are realizing that you can discuss adapting to flooding problems without agreeing on the cause,” he said. “Even conservative politicians like (New Jersey) Gov. (Chris) Christie are willing to say, ‘We are having problems.’ … The reality of this problem is starting to transcend some of the politics.”

Sidebar Elements

Boats tied up at Chandlers Wharf in Portland off Commercial Street on Wednesday, Oct. 23. Nearly $33 million in damage will be done to buildings along the city’s low-lying Commercial Street area by 2050 because of steady sea level rise, a city architects group announced.